Liners provide a soft, flexible interface between a residual limb of an amputee and a hard socket to which a prosthetic device is secured. Such liners are typically made of an elastomeric material such as silicone. Such liners may also be used in connection with orthotic devices. Prosthetic suspension liners are described in prior patents, and may be fabricated of elastomeric or rubber materials, and are used to cushion a post-operative stump or residual limb with respect to a prosthesis that is installed over the residual limb and coupled to the liner, e.g. by a conventional locking device.
Such liners should conform closely with the residual limb, accommodate all surface contours and sub-surface bone elements of the residual limb, and provide a comfortable cushion between the residual limb and the hard socket of the prosthesis that is to be fitted over the residual limb. Various silicone rubber or elastomeric materials are used for suspension liners. Such elastomeric materials having an appropriate hardness/softness, elongation, tensile, and other properties, such as bio-inertness (resulting in no skin reaction), have been successfully used for suspension liners.
The elastomeric forming the liner frictionally engages and remains attached to the skin of a residual limb so that the limb is retained within the prosthetic socket in a comfortable, non-irritating manner. For example, liners may be used for any level of amputation both upper and lower limb. Prosthetic liners are used to cushion the amputee's residual limb from shock during ambulation.
With the advent of vacuum assisted or suction socket systems the residual limb is surrounded in a non-permeable material, and the socket is secured to the limb/liner via a vacuum link. A consequence of reduced or loss of vacuum is the possibility of losing the link between the liner and socket. A loss of linkage could result in the detachment or loss of the prosthesis.
Prior art approaches include applying external vacuum systems to the prosthesis to achieve enhanced suspension between the socket and the amputee. Such a prosthesis normally has four main suspension components. The socket is the rigid or semi-rigid structure that has a shape designed to encompass the residual limb. The liner is a softer interface between the socket and the amputees residual limb. A seal contains the vacuum between the inner surface of the socket and the outer surface of the liner, and a vacuum pump or other means introduces vacuum into the space between the inner surface of the socket and the outer surface of the liner.